Chilli sauces are usually rated using a technique not dissimilar to homeopathy that you can easily try at home. A sample is repeatedly diluted with an equal amount of sugar-water until five trained tasters can no longer taste the chilli. The rating reflects how many times it has had to be diluted to remove all of the "heat".

Mild sauces rate as low as 2500 on this "Scoville" scale, while the hottest chilli in the world rates 1,000,000. Pure capsaicin rates about 15 times that.

Using the new nanotube method, capsaicinoids - capsaicin and related compounds - stick onto the tiny tubes. A chemical reaction is kicked off that oxidises them, and that affects an electric current flowing through the nanotubes in a way that reflects the hotness of the sauce. The output can be converted into Scoville units.

The Oxford team hope to develop cheap disposable versions for use in the food industry. Perhaps they imagine future foodstuffs will come labelled with a numerical measure of how many chilli units are inside.

Chilli testers won't welcome the study, though - the researchers state in their paper that the nanotubes "can be an excellent replacement for the human tasting panel method of determining the Scoville units".

Wednesday, January 02, 2008

Nanofilms from the lab

Talking and thinking about nanotechnology can be hard, because the tiny scales make it tricky to picture what is happening. Here are two good videos that help - they show experiments by researchers at the Technical University of Denmark.

The first is part of a research project trying to make nano-sized components in the same way as larger objects in the workshop. Taken with an electron microscope, it shows a pair of microscopic tweezers plucking a nanotube from where it was grown and placing it somewhere else.

They used an electron microscope and electron-beam etching to make the 8.4 by 12.4-micron calendar on a semi-conducting gallium arsenide wafer coated with plastic. The smallest features are the glass panes on the church windows at about 20 nanometres across. Sadly, you can't open any of the closed windows. Maybe next year.

Proof (if proof were needed) that making quirky, small stuff is a competitive area, Weiss was inspired when researchers at Germany’s Jülich Research Centre received attention for making a 55-micron tall Christmas gingerbread man.

"That’s huge," said Weiss, who immediately gathered his team to do better. He told Chemistry World: "For us, the calendar was a joke – but it is based on serious science."

Nicola Pugno, at the Polytechnic of Turin in Italy, has worked out that covering a suit with a branching "hierarchical structure" of nanotubes should create sufficient inter-molecular force to keep a human nicely suspended from the ceiling.

By separating into ever-smaller bristles the branching nanotubes should be flexible yet rigid enough to produce good adhesion through inter-molecular Van der Waals forces. This is the same trick that let Geckos to climb sheer surfaces like glass with ease.

In the New Scientist article , Pugno discusses the possibility of window cleaners scaling sky-scrapers using a gecko suit as well as an invisible adhesive "cable" made from 4 million individual nanotube fibres.

Wednesday, July 25, 2007

Return of the mechanical computer?

Is the mechanical computer about to make a comeback? It's an interesting possibility that is raised in a paper in the latest edition of the New Journal of Physics. In it, Robert Blick and colleagues at the University of Wisconsin-Madison explain how a fully-mechanical nanoscale computing device might be constructed.

Blick and colleagues suggest that a nanomechanical computer (NMC) could be constructed by linking together lots of nanoelectromechanical single-electron transistors (NEMSETs), which would perform the most basic logical operations. These devices process information using the movement of a nanoscopic pillar (see image, bottom right). Many different NEMSET devices could, in theory, be connected mechanically to form a much larger, more complicated logical circuit, the researchers say.

But Blick and colleagues say a nanomechanical computer could have several key advantages over a silicon computer architecture. It ought to waste less power, should be less vulnerable to electromagnetic interference, and could work at far higher temperatures, the team says.

This could make the mechanical computer of the future ideally suited to use aboard spacecraft, in military devices, and inside high-temperature machinery.

Tuesday, July 17, 2007

Parasitic computing

News that the world's first heat transistor has been built by scientists at the Low Temperature Laboratory at the Helsinki University of Technology, Finland, should be greeted with a cautious welcome.

The device stems from the discovery, almost 10 years ago, that transistors can be switched on and off, not only by injecting a current across them, but also by heating or cooling.

It takes only a short leap of imagination to accept that a similar device might also be able to pump heat, creating a tiny refrigerator. And that's exactly what Olli-Pentti Saira and colleagues seem to have achieved with their heat transistor, details of which were published in Physical Review Letters last week.

Why is it important?

One reason is that heat transistors raise the prospect of a new generation of temperature sensors. But there's a more important and ubiquitous application.

Today, anything that needs to be cooled usually has to be immersed in a coolant to remove unwanted heat. Silicon chips need fans that are many orders of magnitude larger than the transistors they are supposed to cool.

So, the hope is that heat transistors could help by pumping heat away from the places where it is created. Of course, excess heat has to disperse eventually into a heat sink such as the atmosphere. But a transistor could do this more efficiently and more quietly than any computer fan.

But most exciting of all is the possibility that excess heat from conventional transistors could end up providing the power that heat transistors need to do similar job - you could call it parasitic computing. I wonder how efficient a device like that could eventually become.

Tuesday, March 27, 2007

Top tiny creations

A recent story about 'microscopic alphabet soup' created at UCLA got us thinking about all the quirky ways researchers have chosen to demonstrate new micro, nano-scale technology.

Here's a quick list:

1. The UCLA team wanted to show how accurately they could sculpt tiny particles produced in large numbers. So they chose to make the whole alphabet - along with some nice pics showing how these can be manipulated to spell, you guessed it, UCLA. The scale bar in the image to the left is three microns long.

2. Giving props to your own institution is naturally a common theme. One of the most famous examples is these 5nm xenon letters created by Donald Eigler and Erhard Schweizer to show off their new scanning tunnelling microscope way back in 1990. A tiny man made from carbon monoxide molecules was also produced at IBM.

3. Ken Teo of Cambridge University sent me this great image of the New Scientist logo written in carbon nanotubes a while ago. They're 50 nanometres in diameter and 1.5 microns long. The entire logo, from N to t, is 120 microns. Ken has also discovered that forests of nanotubes can be even less sticky than teflon.

4. Researchers at Japanese firm Hitachi decided to make a statement in 1991 when they wrote the message 'Peace 91 HCRL' by knocking sulphur atoms one by one from the surface of a molybdenum disulphide crystal. Not only were the 1.5nm letters smaller than IBM's, the process took place at room temperature instead of minus 263°C. According to Shojiro Asai, deputy general manager of the lab, the researchers who did the work chose the message. "We should hope for peace in 1991 because of the Gulf situation," he said. But they were also sure to put in the initials of the Hitachi Central Research Laboratory. To find out more and for help locating the letters try this link.

5. In 1997, a PhD student at the Cornell Nanofabrication Facility in New York made a "nanoguitar" that's just 10 microns long. It was carved from a single silicon crystal using an electron beam. Each string is about 100 atoms wide and they were plucked using an atomic force microscope. In 2003, he made a fancier version - more pictures and a few recordings of it being played.

6. In August 2005 this badger was made from nanotubes by graduate students from the University of Wisconsin-Madison, US. Their rendering of the university's mascot is about 15 microns across - you could probably get 9,000 of them onto the head of a single pin.

8. And finally... the world's smallest advert. It was positioned on a bee's leg by scientists at the Rutherford Appleton Laboratory, UK. They used vapour deposition to produce the gold advert for the Guiness Book of Records website in 2000, and then moved it to its headline-grabbing location. It was just 100 microns wide.

Of course these are the images that got released to the press. In labs around the world people must have used their bleeding-edge technologies to make structures just to impress their friends. I wonder how many scientists' significant others have received nano-Valentines on Feb 14th? And how can I get one next year?